1. Field of the Invention
The invention to be described in this specification relates to a technique for driving a power supply line in a self-luminous display panel. The invention has embodiments as a semiconductor integrated circuit, a self-luminous display panel module, electronic apparatus, and a method for driving a power supply line.
2. Description of the Related Art
Features of an organic EL (electroluminescence) display panel include not only high contrast but also a wide viewing angle and high response speed. Furthermore, the organic EL display panel needs no backlight light source and thus is suitable to obtain a display panel having smaller thickness. Therefore, the organic EL display panel is attracting attention as the leading candidate of the next-generation flat panel.
A related art is disclosed in e.g. Japanese Patent Laid-open No. 2002-251167.
The organic EL display panel can control the peak luminance level based on the emission time length of an organic EL element OLED. With reference to FIGS. 1A to 1C and 2, this function to control the luminance level will be described below. FIGS. 1A to 1C show the ratios of the emission period to a one-frame period, which is defined as 100%. In the diagram, the length of the hatched bar indicates the emission period length. For example, FIG. 1B shows a state in which 25% of the one-frame period is used as the emission period, and FIG. 1C shows a state in which 50% of the one-frame period is used as the emission period.
The number of emission periods in the one-frame period is not necessarily limited to one but the emission period may be divided into plural periods as long as the total length of the emission period in the one-frame period is the same.
FIG. 2 shows the relationships between the pixel grayscale and the luminance level dependent on the difference in the emission period length. In FIG. 2, the ordinate indicates the luminance level and the abscissa indicates a signal potential Vsig or a drive current Isig corresponding to the pixel grayscale. As shown in FIG. 2, when the emission period length is longer, the peak luminance level can be set to a higher level. That is, a wider variable range of the luminance level can be ensured.
However, the method in which the peak luminance level is varied based on only the length of a single emission period as shown in FIGS. 1A to 1C involve a problem of difficulty in ensuring of both favorable moving image performance and flicker suppression performance. For example, a longer emission period length can provide a higher peak luminance level but involves a problem of the lowering of the moving image response characteristic. On the other hand, a shorter emission period length can enhance the moving image response characteristic but leads to a problem of the lowering of the peak luminance level and a higher degree of visual recognition of flicker.